There are at least two streaks here, in the same trajectory. This glow is later dusk, nautical twilight, while these streaks are stellar in origin. The bright object is Venus.

This being shot in May, the zodiac would appear to be dipping to the northwest. Given that the Chicago skyline was west of the lake, and the railway ran along the Lakeshore back then, this is facing west-northwest.

Kodachrome of that day was either ASA8 or ASA10 speed, which is incredibly slow. Also, Kodachrome has poor reciprocity failure, meaning that it requires much more time to make very long exposures like this. Even time exposures with Kodachrome 64 in 2010 is pretty slow.

(Just to be sure, I pulled up Astroviewer.com's interactive night sky viewer, plugged in May 15, 1943, 8:50p CST, Chicago, and Venus is indeed in the western sky; the dimmer star is probably Theta Aurigae).

Nerd time over.

What is that? Were commercial planes that common in 1943 like tsturm suggested?

[Aircraft running light? Whether military, civilian or interplanetary, it's hard to say. - Dave]

Great composition of light & dark, Jack sure knew how to take great photos. It looks like the boxcar is lit up by an auto's headlights.

[Jack used a floodlight. - Dave]

It's interesting to compare this photo with the nighttime scene in any modern city - nowadays there are so many lights in the office buildings, while back then the offices were pitch black at night.

It seems there is a lit plane flying past the tower on the left...

[This was during World War II. There were blackout regulations in a lot of big cities, though mostly on the East Coast. - Dave]